Advancing/retracting mechanisms are known in the prior art and have been effectively used in a variety of devices, such as writing utensils, erasers, knifes, etc. For example, advancing/retracting mechanisms are used in writing utensils, such as pens, to advance and retract a writing tip from and into a body of the pen. The advancing/retracting mechanism in one such device includes a body, an activation button, a spring and a rotatable cam. A user activates the advancing/retracting mechanism by depressing the activation button into the body of the pen. The activation button includes a plurality of ribs that engage with a plurality of slots in the body of the pen that are oriented parallel to a central axis of the body, thereby restricting the activation button to axial movement within the body of the pen. The activation button further includes a plurality of pointed teeth on an end adapted to engage with the rotatable cam. The rotatable cam similarly includes a plurality of ribs that engage with the plurality of slots, and a plurality of pointed teeth on an end adapted to engage with pointed teeth on the activation button. The plurality of slots prevent rotation and allow axial movement of the rotatable cam during engagement, and when disengaged from the plurality of slots, the rotatable cam is free to both move axially and rotationally. The engagement of the pointed teeth on the activation button and the rotatable cam, causes a bias on the rotatable cam to rotate. More specifically, when the ribs of the activation button and the rotatable cam are aligned with the slots of the body, the pointed teeth on the activation button and the rotatable cam are misaligned, such that the points of the teeth on the activation button abut sides of the teeth of the rotatable cam. Therefore, as the activation button and hence the rotatable cam is depressed into the body of the pen, the activation button and the rotatable cam will axially move along the plurality of slots, during which the rotatable cam has a bias to align its teeth with those of the activation button. Once the ribs on the rotatable cam clear the slots of the body, and is free to rotate, the teeth of the rotatable cam and the activation button will align, thereby rotating the rotatable cam. Once the rotatable cam has rotated (i.e. the teeth of the rotatable cam and the activation button are aligned), the user will remove force from the activation button, which will cause the bias created by the spring to return the activation button to its original position prior to depression. As the activation button retracts, the ribs of the rotated rotatable cam will abut and rest upon a plurality of stop members, thereby causing rotatable cam to remain in the advanced position.
The advancing/retracting mechanism of another such device includes a hollow body having first and second portions, a slider having a pair of guide posts, and a pair of helical slots located in the first portion. More specifically, the pair of guide posts on the slider slidingly engage with the helical slots in the first portion, thereby producing an axial motion of the slider when rotated relative to the first portion. The slider is permitted to move axially, but is rotationally fixed relative to the second portion. Therefore, during rotation of the first and second portions relative to each other, the slider rotates with the second portion, and the engagement of the posts with the slots causes the slider to advance and retract depending on the direction of rotation.